1. Field of the Invention
The present invention relates to a liquid delivery apparatus, and particularly to a liquid delivery apparatus driven by a piezoelectric element.
2. Discussion of Related Art
As a kind of liquid delivery apparatus, there is conventionally known an ejecting apparatus where a plurality of pressure chambers each accommodating a liquid is closed by, for example, a diaphragm which is bonded to and locally deflected by a plurality of piezoelectric elements so as to eject a droplet of the liquid from corresponding nozzles. For instance, such an apparatus is disclosed in JP-A-11-300971, which teaches a head of unimorph type where a recess is formed at an area in a diaphragm so as to oppose to a corresponding one of upper electrodes, so as to increase an amount of displacement of the diaphragm.
The conventional liquid delivery apparatus is so constructed that an area of a piezoelectric element which corresponds to a position of the corresponding pressure chamber and is to be deflected has a laminated structure which is obtained by superposing the piezoelectric element on a diaphragm and bonding the piezoelectric element and diaphragm to each other. Thus, the piezoelectric element and the diaphragm are integrally deformed when the piezoelectric element is driven. According to this arrangement where the piezoelectric element and diaphragm deform integrally at the area corresponding to the pressure chamber, the deformation of the piezoelectric element is restricted by the presence of the diaphragm, leading to an insufficient deformation of the piezoelectric element and accordingly a limited displacement of the diaphragm.